Support SQLAlchemy 1.3 deprecated threadlocal strategy

SQLAlchemy 1.3 has deprecated the threadlocal engine strategy. This
change has the side effect of making the Engine.contextual_connect()
method private, which interferes with our mocking. Depending on the
installed version of SQLAlchemy, mock this method differently.

See:
- https://docs.sqlalchemy.org/en/latest/changelog/migration_13.html

Author: jeancochrane

pytest_flask_sqlalchemy/fixtures.py

@@ -3,6 +3,7 @@
 
 import pytest
 import sqlalchemy as sa
+from packaging import version
 
 
 @pytest.fixture(scope='module')
@@ -95,7 +96,14 @@ def _engine(pytestconfig, request, _transaction, mocker):
     engine = mocker.MagicMock(spec=sa.engine.Engine)
 
     engine.connect.return_value = connection
-    engine.contextual_connect.return_value = connection
+
+    # Threadlocal engine strategies were deprecated in SQLAlchemy 1.3, which
+    # resulted in contextual_connect becoming a private method. See:
+    # https://docs.sqlalchemy.org/en/latest/changelog/migration_13.html
+    if version.parse(sa.__version__) < version.parse('1.3'):
+        engine.contextual_connect.return_value = connection
+    else:
+        engine._contextual_connect.return_value = connection
 
     # References to `Engine.dialect` should redirect to the Connection (this
     # is primarily useful for the `autoload` flag in SQLAlchemy, which references

setup.py

@@ -19,7 +19,8 @@ def readme():
     install_requires=['pytest>=3.2.1',
                       'pytest-mock>=1.6.2',
                       'SQLAlchemy>=1.2.2',
-                      'Flask-SQLAlchemy>=2.3'],
+                      'Flask-SQLAlchemy>=2.3',
+                      'packaging>=14.1'],
     extras_require={'tests': ['pytest-postgresql']},
     classifiers=[
         'Development Status :: 4 - Beta',